Windows are employed in all types of construction, whether it be private, commercial, stationary or mobile, to provide for the desired transmission of visible light. At times it is desirable to be able to reduce or prevent light transmission through such windows. The common technique employed to accomplish this purpose is the use of shades, blinds, draperies and other opaque materials to cover the windows. In some types of window installation, these techniques present problems. This would be particularly true of larger windows or inaccessible windows, such as in overhead skylights.
The prior art discloses a further technique. In U.S. Pat. No. 2,783,682 there is disclosed a window assembly comprising two parallel spaced apart panes of glass with the inner surface of one pane being scalloped or fluted to disperse transmitted light rendering the assembly translucent rather than transparent. The assembly is rendered transparent by filling the space between the panes with a liquid having the same refractive index as glass. Translucency is restored by removing the fluid. A modification of this technique is described in U.S. Pat. No. 3,711,189. In this patent the window assembly comprises two parallel spaced apart panes of glass. To the inner surface of one of the panes is attached a fabric of closely woven transparent fibers. While the fibers per se are transparent the woven fabric is not, for obvious reasons, and, thus, the entire assembly is rendered translucent to opaque in the transmission of visible light. In this case the assembly is rendered transparent by filling the space between the panes with a liquid having the same refractive index as that of the transparent fibers.
While these two systems are, in general, operable, improvements in two respects are desirable. First, economy in operation suggests some means of reducing the amount of fluid required. In these prior art assemblies, the amount of fluid employed must be such to completely remove or fill the surface irregularities of the translucent element. Merely wetting the surface would not be sufficient. Second, the irregular surface of the translucent element hampers the clean and quick removal of the fluid when a change from transparency to translucency is desired. Droplets of the fluid will tend to cling to the irregular surfaces or be trapped in interstices.
It is an object of this invention to provide an improved window assembly which can be quickly, efficiently and reversibly changed from a substantially uniform state of translucency to a substantially uniform state of transparency. Other objects will become apparent from the description of the invention.